This invention relates generally to the field of materials or fabrics and, more particularly, to high strength, compliant fabrics that stretch freely, are easily stowable, tough, and have specific elongation limits. Such fabrics are used in automotive air bag material, awnings, tents, portable structures, active wear garments, fatigues, and deployable, inflatable ballistic protective systems.
Fabrics that are high strength and tough are either made from high performance fibers or are a combination of films or plastic sheet materials and reinforcing fibers. Todays high performance fibers include Dacron, Nylon, aramids such as Kevlar, graphite (low to high modulus), ultra high molecular weight polyethylenes such as Spectra, and filamentary thermoplastic product forms such as PEEK, Ryton, PBI, Radel X, and assorted liquid crystal polymers such as Xydar, Victrex, and PBO. As reinforcements for structural materials, these fibers are combined and processed into a variety of textile materials. Usually a matrix material known as a binder, is combined with the fibrous reinforcement to produce a composite product which is tailored to meet specific performance requirements. An example of this kind of product is ballistic cloth. Ballistic cloth laminates are often bound with a polymer.
When films and plastic sheet materials require additional strength, the usual approach is to reinforce them with a fiber. This strengthening technique produces a material that is usually strong, but is also stiff and inelastic. The tendency in this type of fabric is for the film or sheet to tear or rip away from the reinforcement fibers when the material is overstretched. An example of this type of product is the tarpaulin commonly used in the trucking industry and sold in sporting good stores.
Reinforcing or reinforcing mesh is commonly fabricated on looms that lock fiber intersections by means of crossing a parallel fiber over and the perpendicular fiber beneath. Additionally, knitted textile products may have these fiber intersections fixed with a loop or lock stitch. Both of these types of reinforcing are weakened due to fiber crossover or the fibers being out of plane.
Other materials that exhibit elastic properties are of two types; those that are either elastomeric films or rubber compound sheets, or those that are basically multiple bands of slit sheet rubber overwrapped with organic fiber yarn that can be woven into an elastic fabric. Both of these types of materials are used for their ability to stretch and comply, yet return to their original size and shape when the tension is released or relaxed.
Elastic materials made from elastomeric films or rubber compound sheets prior to the present invention suffer from the disadvantage that when over-stretched, they rapidly begin thinning, and thereafter, tear or rupture. To inhibit this failure, elastomeric film or sheet products must be designed very conservatively; and are usually overly thick, bulky and therefore relatively heavy.
The elastic materials that use elastic thread hanks, which are basically multiple bands of slit sheet rubber, such as a latex based elastomer, stretched or tensile loaded and overwrapped with organic fiber yarn, suffer from the disadvantage that their degree of over-stretching is limited by the strength of the yarn. Once overstretched these fabrics lose their ability to return to their original shape. Materials commonly used in the waistbands of undergarments and shock cords are examples of this kind of fabric.
It will be appreciated from the foregoing that there has long been a need for improvement in the field of stowable deployable elastomeric material. In particular, there has been a need for an elastomeric material that will stretch freely, and yet have elongation limits, while exhibiting high ultimate tensile strength, stowability, and toughness. The present invention satisfies this need.